Centrifuge

ABSTRACT

A centrifuge for treating a fluid, particularly a fluid containing heavier corpuscles in suspension, such as blood, includes a rotor rotatable about a spin axis and a motor for operable to rotate the rotor. A flexible tube extends through the rotor and has end portions extending from the ends of the rotor coaxially with the spin axis, the flexible tube, between the end portions thereof and within the rotor, being bent radially outwardly of the spin axis to form a bend with the radially outermost bend portion forming the treatment chamber. The tube is supported for rotation about its own axis independently of rotation of the rotor, and injection means are provided to supply fluid to be treated to the treatment chamber, with discharge means being connected to the tube to discharge treated fluid from the treated chamber into receptacles in a dish. Selectively operable brakes are engageable with the tube to cause the tube, during spinning of the rotor, to be decelerated to rotate about its own axis relative to the rotor.

United States Patent m Westberg et al.

I [111 3,817,449 l4 l June 18, I974 CENTRIFUGE [75] Inventors: Johan Erik Hayden Westberg,

\ Lidingo; Hans Peter Olof Unger,

Stockholm, both of Sweden [73] Assignee: AGA Aktiebolag, Lidingo, Sweden [22] Filed: Feb. 15, 1972 [21] Appl. No.: 226,591

[30] Foreign Application Priority Data Primary Examiner-George H. Krizmanich Attorney, Agent, or Firm-McGlew and Tuttle 57 ABSTRACT A centrifuge for treating a fluid, particularly a fluid containing heavier corpuscles in suspension, such as blood, includes a rotor rotatable about a spin axis and a motor for operable to rotate the rotor. A flexible tube extends through the rotor and has end portions extending from the ends of the rotor coaxially with the spin axis, the flexible tube, between the end portions thereof and within the rotor, being bent radially outwardly of the spin axis to form a bend with the radially outermost bend portion forming the treatment chamber. The tube is supported for rotation about its own axis independently of rotation of the rotor, and injection means are provided to supply fluid to be treated to the treatment chamber, with discharge means being connected to the tube to discharge treated fluid from the treated chamber into receptacles in a dish. Selectively operable brakes are engageable with the tube to cause the tube, during spinning of the rotor, to be decelerated to rotate about its own axis relative to the rotor.

8 Claims, 2 Drawing Figures CENT RIFUGE FIELD AND BACKGROUND OF THEINVENT'ION The invention relates to a centrifuge for the consecutive treatment of portions of fluids, particularly of fluids containing heavier corpuscles in suspension. The centrifuge is primarily intended for treating blood samples, for instance by first washing-the sample with a washing fluid and then mixing it with a liquid reagent. An example of such a treatment is the serological test known as a Coombs test, which is used for finding out whether red blood cells agglutinate after having been mixed with AHG serum anti-human-globulin serum). Before they are mixed with the AHG serum the blood corpuscles must be repeatedly washed with a solution of salt to remove unwanted protein'substances. After washing the washing fluid containing the washed out protein substances is separated from the blood cells by centrifuging. When they are being'washed and when they are mixed with the antiserum the blood corpuscles must be well shaken in the washing fluid, respectively antiserum.

In automatic analysers, such as automatic instruments for blood group determination in which blood samples of different donors are treated in rapid succession and subjected to varying analyses, it has been found difiicult to carry out those analyses which involve centrifuging the samples. For instance, the short time available for each sample and the limited volume of each sample (e.g. 1 minute; 1 2 cc.) present difficult problems. Another difficulty resides in the necessity of preventing a later sample from being contaminated by residues from a preceding sample.

SUMMARY OF THE INVENTION The present invention seeks to solve these problems. For this purpose the centrifuge of the invention is constructed as described hereinafter and is characterised not only by its ability effectively and rapidly to treat tical spin axis and drivable by a motor 15 through a belt transmission 16 at a high speed, such as 20,000 rpm. The centrifuge is bodily movable vertically and horizontally in relation to a sample holder 17 containing three dishes 18, 19 and 20. Dish 18 contains the blood sample that is to be treated, dish 19 contains the washing fluid (a physiological solution of common salt), whereas dish 20 initially remains empty, its purpose being to receive the blood sample after its treatment. Naturally it would also be possible to mount the centrifuge so that it is fixed and to make the sample holder 17 horizontally and/or vertically movable.

A smooth plastics tube 21, preferably consisting of polytetrafluoroethylene (also sold under the registered name Teflon), extends through the rotor 14. At the ends of the rotor the tube is coaxial with the rotor, whereas between the ends it includes a bend 22 in a diametral plane. Coaxially extending through the length of the tube 21 is an inner flexible tube 23 which is therefore likewise coaxial with the rotor at both rotor ends and curved at 24 in a diametral plane inside the rotor. The tube 23 projects from the top as well as the bottom end of the rotor 14 and is rotatable in relation to the rotor about its own axis which flexibly arches ineven small volumes of fluid without any risk of contam- I ination of either sample or the reagents, but also by the fact that it can be of very simple and compact design.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE PREFERRED I EMBODIMENT The illustrated centrifuge is intended for the performance of a Coombs test, but it will be understood that the centrifuge is not intended tobe limited to this particular application. Examples of other treatments that may be performed will be mentioned later.

The centrifuge shown in the drawing comprises a body or structure generally indicated by 10 and composed of an upper block 11, a lower block 12 firmly connected thereto and a cap 13 firmly attached to the.

latter. The lower block 12 and the cap 13 form a housing mounting a rotor 14 which is rotatable about a verside the rotor. The tube 23 is also of plastics construction and preferably made of polypropylene which has excellent fatigue-resisting properties besides being smooth so that no major friction will impede its rotation. However, provided no external braking moment is applied to this tube 23, it will participate in the spin of the rotor without itself rotating in relation thereto.

The downwardly projecting portion of the inner flexible tube 23 extends through the cap 13 into a tubular guide element 25. The bottom end of the tube is attached to a capillary 26 by a sealing joint and this capillary projects from the bottom end of the guide element 25. The bottom end of the cap 13 contains a bearing for the bottom end of the rotor 14 as well as a brake 27. The latter consists of a spring wire or wire ribbon 28 which is coiled several times round the tube 23 between rings 29 to which the ends of the wire are attached. By twisting one of the rings 29 relative to the other the coils of wire or ribbon 28 can be pulled tight aroundthe tube to stop it from rotating. Functionally this brake is'therefore the equivalent of a conventional band brake. Turning of the ring is preferably effected by a lever (not shown) which projects from the cap 13.

The upwardly projecting end of the flexible tube 23 is suitably mounted in the lower block 12. Moreover, the upper end of the tubewidens into a bearing bush 30 formed with a radially inwardly projecting flange at the top. This bearing bush 30 is afi'rxed to the widened end of the flexible tube so that it cannot rotate in relation thereto and it locates the end of the tube in the axial as well as in the radial direction. It is surrounded by a brake 31 similar to the brake 27 and it can be activated together therewith to stop the tube 23 from rotat- At the upper end of the flexible tube 23 the centrifuge is provided with means for the admission into the tube of a reagent, which in the present instance is assumed to be AHG serum (Coombs serum). These means, which are shown on a larger scale in FIG. 2, comprise a syringe 32 filled with the AHG serum and a flanged sleeve 33 of elastic material. This sleeve 33 is located in the lower block 12 and extends downwards into the upper end of the bend 24. It is closed at one end, whereas the other end where the flange is located is open. The hollow interior comprises an upper wider portion and a bottom narrower portion. The closed bottom end of the narrower portion contains a selfclosing slit 34. The capillary tube 35 of the syringe 32 enters the bottom narrower portion which in sealing manner tightly embraces the capillary tube. When the plunger 36 of the syringe is pushed down, AHG serum is forced through the self-closing slit 34 into the bend 24 of the tube. The upper wider portion of the sleeve 33 is enlarged to form a chamber 37 surrounding the capillary 35. This chamber communicates through an opening 38 in the sleeve wall with the interior of the flexible tube 23 and, through a length of tubing 39 surrounding the capillary, with a channel 40 in the upper block 11. The outside of the length of tubing 39 forms a seal in the sleeve 33 as well as in the block 11. The channel 40 is connected to a pump (not shown) which permits a vacuum or gauge pressure to be generated inside the channel and hence in the interior of the tube 23. As will be apparent, more particularly by reference to FIG. 2, one side of the sleeve 33 slightly bulges in the region of the opening 38 so that the gap between this opening and the inside of the tube 23 is very small. Consequently a fluid in the enlarged upper end of the tube can be effectively drawn into the channel even when the tube rotates.

For depressing the plunger 36 of the syringe 36 there is provided a screw 41 which works in a holder 42 attached to block 11, and whichis adapted to discharge a dose of AHG serum when it is turned through a prescribed angle. This is done by a suitable operating device, not shown, via a gear wheel 43 which is axially movable on the screw but rotatably fast thereon. The screw, when operated, slightly depresses the plunger and thus causes a predetermined volume (a few drops) of the serum to be squeezed out through the capillary 35 and the slit 34. The holder 42 is easily detachably mounted on the block 11 to permit the syringe to be replaced. At the same time the block 11 containing the syringe 32 is easily detachable from the block 12 to permit it to be kept in a refrigerator when the centrifuge is not in use.

It will be noted that rotor 14, tubes 21 and 23, capillary 26, bearing bush and one of the rings 29 are rotatably mounted relative to the stationary upper block 11, lower block 12 and cap 13.

The procedure for performing a Coombs test in the described centrifuge is as follows:

The brakes 27 and 31 are first released to permit the flexible tube 23 to participate in the rotation of the spinning rotor 14, without itself rotating in relation to the rotor. The centrifuge or the sample holder 17 are then vertically moved until the end of the capillary tube 26 dips into the blood dish 18. The pump associated with channel 40 causes the blood to be sucked into the tube 23 in which it is held in the culminating arch of the bend 24 by centrifugal forces. This curved portion of the tube thus forms a chamber in which the treatment takes place. Centrifugal force immediately packs the blood corpuscles inside the bend at the radially extreme outer end of this treating chamber.

The centrifuge and/or the sample holder 17 is/are then moved vertically and horizontally until the capillary tube 26 dips into the washing fluid in dish 19 so that a predetennined volume of this fluid is sucked up the tube to be retained in the bend 24.

After the washing fluid has been drawn into the treating chamber the brakes 27 and 31 are engaged for stopping the tube 23 from rotating or at least for retaining the tube so that it will now rotate at a slower speed than the rotor 14. The portion of the tube 23 forming the treating chamber will then revolve about the spin axis of the rotor 14 and at the same time rotate in relation to the rotor about its own axis. This means that the centrifugal force acting at any point in this position of the tube will fluctuate, changing in direction towards and away from the point in such manner that in the course of each revolution the centrifugal force will act once away from the tube axis towards the point and then away from the point towards the tube axis. The blood corpuscles which had formerly been bunched together against the wall of the treating chamber will therefore now be dispersed and forced to move to and fro in the fluid. The outermost part of the treating chamber is located at a radial distance from the spin axis of the rotor which is relatively small when measured against the internal diameter of the flexible tube. The greatest distance may for instance be twice the internal diameter of the tube and this would mean that the centrifugal force at every point on the inside wall of the tube in the culminating arch of the tube bend 24 will fluctuate in the course of each revolution between 50 and percent of its maximum value (which may be as high as say 1,000 g).

The violent shaking thus experienced by the blood corpuscles due to the fluctuation of the centrifugal force, in conjunction with the tendency of the liquid to participate in the rotation of the flexible tube in relation to the spin of the rotor has the result of causing the corpuscles to be very rapidly (a washing time of a few seconds is sufficient) and effectively washed by the washing fluid and separated from the unwanted protein substances. Contrary to conventional washing centrifuges all the blood corpuscles will be reliably washed since no blood corpuscles can adhere to the wall of the treating chamber.

At the end of a washing period of a few seconds the brakes 27 and 31 are released, allowing the tube 23 to revolve again together with the rotor 14 and to stop rotating independently thereof. The blood corpuscles will then be subjected to a continuous centrifugal force acting towards one and the same point inside the tube. Since the blood corpuscles need not move very far (a few millimetres) outwards before reaching the wall of the treating chamber only a few seconds of centrifuging are needed to pack them all against this wall.

A fresh quantity of washing fluid is then drawn up into the treating chamber. The fresh fluid displaces the previously used washing fluid which is sucked out through the channel 40. The channel 40 can be continuously maintained at vacuum pressure and when the fresh washing fluid is to be drawn in, the rotor may be braked to prevent centrifugal forces from impeding the suction efiect. The described washing cycle is then repeated until the washing of the blood corpuscles is completed.

The washing fluid which is sucked out of the tube 23 into channel 40 flows into the channel through the opening 38 in the sleeve 33, the chamber 37 and the length of tubing 39. The inwardly projecting flange of the bearing bush 30 and the closeness of the opening 30 to the inside of the tube prevent the washing fluid from leaving through the upper end of the tube 23 and from thus entering the tube bearing.

When washing has been completed the centrifuge can be stopped (braked down to a low speed), the washing fluid being sucked out and the washed blood corpuscles remaining at the tube wall where they had been packed together by the centrifugal force. The centrifuge is then restarted and the syringe 32 is operated to inject AHG serum through the slit 34 which functions as a non-return valve and thus prevents the washing fluid from entering the sleeve 33 when it is being drawn out of the treating chamber. AHG serum is very sensitive to contamination. Since the slit 34 is at the end of the bend 24 in the tube the injected serum is immediately driven into the treating chamber by the centrifugal force.

The brakes 27 and 31 are then reengaged, causing the AHG serum to be mixed with the blood corpuscles in the treating chamber. When the capillary 26 has been moved over the empty dish 20 in the sample holder, the centrifuge motor is stopped, allowing the fluid from the treating chamber to flow downwards through the tube. A slight gauge pressure is applied to the channel 40 and hence to the interior of the tube 23 to assist the discharge of the fluid into the dish for further analysis.

Before the next sample is treated a fresh volume of washing fluid is drawn up through the tube to flush out any residues from the preceding sample. For this operation the centrifuge motor may remain stopped.

If desired or necessary several centrifuges of the kind illustrated in the drawing may be combined in an assembly for simultaneously treating several samples. All the centrifuges of such a unit may be driven by the same motor, the rotor of the centrifuge that is directly driven by the motor driving the rotor of the next centrifuge by means of a belt and so forth. The centrifuge assembly can thus be very compactly designed.

The invention has above been illustratively described with special reference to the Coombs test, more particularly a variant of this test known as the indirect Coombstest. As already indicated the proposed centrifuge can also be used for other'treatments, such as an indirect Coombs test in which serum of the blood that is to be examined is contacted with red blood cells of group O Rh and then treated with AHG serum as above described. Another example is the separation of blood corpuscles and blood plasma followed by washing of the blood corpuscles.

What is claimed is:

1. In a centrifuge for treating a fluid, particularly a fluid containing heavier corpuscles in suspension, such as blood, including rotor means with a chamber for performing the treatment of a fluid therein and means for admitting fluid to be treated into the chamber during spinning of the rotor means, the improvement comprising, in combination, a rotor; means mounting said rotor for rotation about a spin axis; driving means operable to rotate said rotor; a flexible tube extending through said rotor and having end portions extending from the axially opposite ends of said rotor coaxially with said spin axis, and said flexible tube, between said end portions thereof and within said rotor, being bent radially outwardly ofsaid spin axis to form a bend with a radially outermost bend portion forrning the treatment chamber; means supporting said tube for rotation about its own axis independently of rotation of said rotor; means connected to said flexible tube for supplying fluid to be treated to said treatment chamber and for discharging treated fluid from said treatment chamber; and means selectively engageable with said tube to cause said tube, in the spinning rotor, to rotate about its own axis relative to said rotor.

2. A centrifuge according to claim 1 in which the tube is made of a plastics material.

3. A centrifuge, according to claim 1, in which said means selectively engageable with said tube comprises brakes engageable with both said end portions of said tube extending from the ends of said rotor.

4. A centrifuge, according to claim 1, in which the tube is made of polypropylene.

5. A centrifuge, according to claim 1, including a tubular guide fixedin said rotor and consisting of a plastics; said flexible tube extending concentrically through said tubular guide.

6. A centrifuge, according to claim 5, in which said tubular guide consists of polytetrafluoroethylene.

7. A centrifuge, according to claim 1, in which said spin axis of said rotor is substantially vertical; a terminal tube connected to the bottom end of said flexible tube; a receptacle for fluid adjacent said terminal tube, said terminal tube being adapted to be dipped into said receptacle; and pump means connected to the upper end of said flexible tube for drawing up fluid from said receptacle through said terminal tube into said treating chamber and for expelling fluid from said treating chamber.

8. A centrifuge, according to claim 7, including plural said receptacles for fluid; said plural said receptacles as a unit and said terminal tube being movable relative to each other for dipping of said terminal tube into a selected one of said plural receptacles. 

1. In a centrifuge for treating a fluid, particularly a fluid containing heavier corpuscles in suspension, such as blood, including rotor means with a chamber for performing the treatment of a fluid therein and means for admitting fluid to be treated into the chamber during spinning of the rotor means, the improvement comprising, in combination, a rotor; means mounting said rotor for rotation about a spin axis; driving means operable to rotate said rotor; a flexible tube extending through said rotor and having end portions extending from the axially opposite ends of said rotor coaxially with said spin axis, and said flexible tube, between said end portions thereof and within said rotor, being bent radially outwardly of said spin axis to form a bend with a radially outermost bend portion forming the treatment chamber; means supporting said tube for rotation about its own axis independently of rotation of said rotor; means connected to said flexible tube for supplying fluid to be treated to said treatment chamber and for discharging treated fluid from said treatment chamber; and means selectively engageable with said tube to cause said tube, in the spinning rotor, to rotate about its own axis relative to said rotor.
 2. A centrifuge according to claim 1 in which the tube is made of a plastics material.
 3. A centrifuge, according to claim 1, in which said means selectively engageable with said tube comprises brakes engageable with both said end portions of said tube extending from the ends of said rotor.
 4. A centrifuge, according to claim 1, in which the tube is made of polypropylene.
 5. A centrifuge, according to claim 1, including a tubular guide fixed in said rotor and consisting of a plastics; said flexible tube extending concentrically through said tubular guide.
 6. A centrifuge, according to claim 5, in which said tubular guide consists of polytetrafluoroethylene.
 7. A centrifuge, according to claim 1, in which said spin axis of said rotor is substantially vertical; a terminal tube connected to the bottom end of said flexible tube; a receptacle for fluid adjacent said terminal tube, said terminal tube being adapted to be dipped into said receptacle; and pump means connected to the upper end of said flexible tube for drawing up fluid from said receptacle through said terminal tube intO said treating chamber and for expelling fluid from said treating chamber.
 8. A centrifuge, according to claim 7, including plural said receptacles for fluid; said plural said receptacles as a unit and said terminal tube being movable relative to each other for dipping of said terminal tube into a selected one of said plural receptacles. 